Lab-on-a-Chip Technology
Publisher: Caister Academic Press
Editor: Keith E. Herold and Avraham Rasooly
Publication date: 2009
ISBN: 978-1-904455-46-2 (Volume 1)
ISBN: 978-1-904455-47-9 (Volume 2)

"a comprehensive view on state of the art LOC technologies ... Overall the double volume represents a comprehensive and felicitous compendium of lab-on-a-chip technologies and applications not only for the beginner going to get started development experimentally in a fast growing and innovative technology. But also the skilled specialist staying in the commercial arena might find a hugely satisfying compilation of state of the art LOC technologies and new ideas for sure. ... All in all 'Lab-on-a-Chip Technology' is a very useful reading for everyone who is interested in development and production of LOC devices" read more ...

from Rolf G. Werner in Arzneimittel-Forschung/Drug Research (2009) 59: 672-673.

Further reading: Lab-on-a-Chip Technology

Labels: Lab-on-a-Chip, Lab-on-a-Chip Technology, LOC

It is a challenge to fully describe the fast-moving field of LOC. However, in a recent publication Herold and Rasooly (Eds) present descriptions of some of the many types of LOC, including fabrication and application details, and give the reader a sense of the range of LOC technologies and the enormous potential that these devices possess.

The main types and the critical elements of LOC systems are discussed from both theoretical and experimental points of view, with special emphasis on technical and experimental detailed that may enable the reader to reproduce the LOC system described and conduct similar experiments. The huge range of applications in molecular biology and molecular diagnostics and testing are explored in depth.

from Herold and Rasooly (Eds) in Lab-on-a-Chip Technology

Further reading:

• Lab-on-a-Chip Technology (Vol. 1)
• Lab-on-a-Chip Technology (Vol. 2)
• Molecular Biology recommended reading

Labels: lab on a chip, Lab-on-a-Chip Technology, LOC

In general LOC systems can be divided into three main categories based on materials and the fabrication technologies used for those materials: polymer systems, glass systems, and silicon systems. Silicon based LOC systems utilize fabrication techniques that grew out of integrated circuit (IC) fabrication technologies. Notable properties of silicon include its electrical conductivity and the wealth of techniques that have been developed for fabrication, surface treatment, and bonding.

Polymer based LOC systems are a more recent development and there exist many fabrication methods, depending on the polymer used. PDMS (polydimethylsiloxane) is sold as a twocomponent liquid that hardens into a rubbery solid when mixed together. PDMS can be used with a surface patterned master to create half of an LOC device which is then completed by sealing the PDMS to a cover (e.g. to a glass slide). The surface patterned master can be micromanufactured from silicon or via soft lithography using a light sensitive mould material (e.g. SU-8). Many other manufacturing methods exist for polymers including embossing, lamination, injection moulding, laser machining, as well as all of the tradition direct machining methods (e.g. drilling or milling).

Glass-based LOC system have the advantage that more is known about biochemical interactions with glass than with any other material. Many surface treatments exist for glass, and it has excellent thermal and optical properties. However, glass is more difficult to machine and designs based on glass need to adapt to the limited machining methods available.

from Herold and Rasooly (Eds) in Lab-on-a-Chip Technology (Vol. 2)

Further reading:

• Lab-on-a-Chip Technology (Vol. 1)
• Lab-on-a-Chip Technology (Vol. 2)
• Molecular Biology recommended reading

Labels: lab on a chip, Lab-on-a-Chip Technology, LOC

Liquid flow is an essential element of most LOC systems. Liquid flow can be single-phase flow through microchannels or multi-phase flow of droplets on a surface. For single phase flow, the flow can be pressure driven, in which the pressure driving force is supplied by an external pump, or the fluid can be pumped by electroosmotic means where the motion of liquid is induced by an applied axial potential along a capillary tube or microchannel. Electroosmotic pumping depends on the electric double layer that forms in an electrolyte adjacent to a charged surface.

Alternately, individual droplets can be moved and manipulated on a surface (e.g. combined, separated or transported) by electric fields. Droplets form on a surface because the geometry of a droplet minimizes the energy of the system (including the energy of the liquid surface, exposed to the vapour phase, and the energy of the attraction between the liquid and the solid surface). Droplets can be manipulated on a surface in two different ways: 1) electrowetting, and 2) dielectrophoresis. Both of these techniques are actuated by manipulating electric fields around the droplets.

Electrowetting is based on the attractive forces between a solid surface and a liquid. When the attraction between the liquid and the solid surface is weak (hydrophobic for an aqueous system), then the droplet tends toward a spherical shape due to the dominance of surface tension energy. The surface force interaction with the fluid (i.e. the hydrophobicity) can be controlled by electric fields (electrowetting).

Dielectrophoresis requires alternating (AC) fields which induce a dipole in a discrete droplet. The droplet then experiences a net force due to the induced dipole when the frequency of the AC field is selected appropriately. Dielectrophoresis can be used to manipulate droplets on a surface using an array of surface electrodes, similar to that required for electrowetting.

from Herold and Rasooly (Eds) in Lab-on-a-Chip Technology (Vol. 2)

Further reading:

• Lab-on-a-Chip Technology (Vol. 1)
• Lab-on-a-Chip Technology (Vol. 2)
• Molecular Biology recommended reading

Labels: lab on a chip, Lab-on-a-Chip Technology, LOC

LOC systems can be miniaturized so that they can be integrated into various pieces of equipment in the medical, industrial, military and public safety fields. Miniaturization can enhance utility in many ways including allowing portability for field applications, providing multiple assays in one instrument (e.g. blood analyser for medical offices), and minimizing expensive reagents.

from Herold and Rasooly (Eds) in Lab-on-a-Chip Technology (Vol. 2)

Further reading:

• Lab-on-a-Chip Technology (Vol. 1)
• Lab-on-a-Chip Technology (Vol. 2)
• Molecular Biology recommended reading

Labels: lab on a chip, Lab-on-a-Chip Technology, LOC, miniaturization

LOC-based diagnostics can be used for point of care testing where state-of-the-art molecular analysis is required without requiring a state-of-the-art laboratory. Diverse biomedical applications and biohazard detection can be carried out in the field. Biomedical applications include medical screening, testing and diagnostics at point of care by primary care providers. Biohazard detection, including pathogens and toxins, encompasses applications in food testing, public health, and biosecurity.

LOC systems can be used for a variety of analytical applications including DNA amplification and analysis, quantitative immunoassays, enzymatic activity assays and other analytical approaches which are done today mainly in centralized, dedicated laboratories with complex and expensive equipment by highly trained personnel. Rapid LOC analysis can provide immediate interactive information to health care providers that can be incorporated into the planning of patient care. LOC-based diagnostics have the potential to improve the rates of earlier detection of cancer and other diseases with attendant improved prognosis. LOC technologies are projected to be extremely useful for enhancing health care delivery in the community setting and to underserved populations especially in remote areas.

from Herold and Rasooly (Eds) in Lab-on-a-Chip Technology (Vol. 2)

Further reading:

• Lab-on-a-Chip Technology (Vol. 1)
• Lab-on-a-Chip Technology (Vol. 2)
• Molecular Biology recommended reading

Labels: diagnostics, lab on a chip, Lab-on-a-Chip Technology, LOC, molecular diagnostics

LOC systems have several potential advantages over other analytical approaches, especially the ability to perform complex analytical chemistry operations without a laboratory. This has the potential to allow samples to be analysed at the point of need rather than at a centralized laboratory.

Inherent advantages of LOC systems The laminar flow behaviour of liquids in typical miniaturized LOC systems allows better control of concentrations and other reaction conditions. Thus, it can reduce the time taken to synthesize and analyse samples, and improve the quality of the product. Miniaturized LOC systems typically require small reagent volumes which can reduce costs of testing and reduce the amount of chemical waste. Small sample sizes can also be a disadvantage because they may not always represent the average condition of a larger reservoir from which they are taken.


from Herold and Rasooly (Eds) in Lab-on-a-Chip Technology (Vol. 2)

Further reading:

• Lab-on-a-Chip Technology (Vol. 1)
• Lab-on-a-Chip Technology (Vol. 2)
• Molecular Biology recommended reading

Labels: lab on a chip, Lab-on-a-Chip Technology, LOC

In the early 1960s, several research groups started working on miniaturized silicon sensors. An early integrated lab on a chip (LOC) device was a complete gas chromatograph on a single 'chip' developed at Stanford University and published in 1979. This new tool was 'expected to find application in the areas of portable ambient air quality monitors, implanted biological experiments, and planetary probes'. The expectations for LOC have been realized repeatedly in the laboratory and commercial applications are beginning to be realized (Herold and Rasooly 2009. Lab-on-a-Chip Technology. Caister Academic Press ISBN: 978-1-904455-47-9).

In the 1980s and 1990s the LOC field moved rapidly and in the last decade approximately 3500 LOC related publications are indexed in Pubmed describing numerous fabrication methods and new applications using a broad array of technologies. The trend is towards more complex integrated multi-analyte LOC systems capable of more comprehensive analyses, utilizing advances in electronics and microfabrication that enable miniaturization and broader capabilities. The newest generation of LOC systems includes a miniaturized chip for isolation of rare circulating tumour cells in cancer patients and complex LOC devices utilizing valving technologies that provide dense fabrication and parallel pneumatic actuation of hundreds of valves.

Bibliography:

1. Lab-on-a-Chip Technology: Fabrication and Microfluidics
2. Lab-on-a-Chip Technology: Biomolecular Separation and Analysis

Labels: lab on a chip, Lab-on-a-Chip Technology, LOC